RU2465045C2 - System for production of polyester with reactor of esterification without mixing - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to method (versions) and apparatus for esterification of polyester in fused phase. Reaction medium is subjected to esterification in vertical elongated reactor. Reactor represents a tank with fluid inlet and, at least, two separate outlets, one for fluid reaction medium discharge and another one for bypass vapor discharge. Vapor discharge is arranged above fluid discharge while fluid inlet is arranged under fluid discharge. Esterification reactor allows heating reaction medium without mechanical mixing or with mechanical mixing of, at least, 50 percent of said reaction medium.

EFFECT: improved operating characteristics and flexibility compared to reactors with continuous mixing of prior art.

19 cl, 3 dwg

Description

BACKGROUND

FIELD OF THE INVENTION

This invention relates to a system for the production of polyesters in the molten phase. In another aspect, the invention relates to an esterification system using a vertical elongated esterification reactor, requiring little or no mechanical stirring.

Description of the Related Art

Polymerization in the molten phase can be used to produce a wide variety of polyesters, such as, for example, polyethylene terephthalate (PET). PET is widely used for beverage containers, food and other containers, as well as in synthetic fibers and resins. Advances in processing technology, coupled with increased demand, have led to a growing competitive market for the production and sale of PET. Therefore, a cheap, highly efficient method for producing PET is required.

In general, production capabilities for producing polyester in the molten phase, including those already used for producing PET, involve the use of an esterification step and a polycondensation step. In the esterification step, polymeric raw materials (i.e., reactants) are converted to polyester monomers and / or oligomers. In the polycondensation step, the polyester monomers leaving the esterification step are converted to a polymer product having the desired final chain length.

In the most common manufacturing processes for producing the polyester in the molten phase, esterification is carried out in one or more mechanically stirred reactors, such as, for example, continuous stirred tank reactors (KLNP). However, CRNP and other mechanically stirred reactors have a number of disadvantages that can lead to increased financial costs, working time and / or repair and maintenance costs throughout the production of polyester. For example, mechanical agitators and various control and measuring equipment, usually associated with KLNP, are complex, expensive and may require extensive maintenance and repair. In addition, common heat-transfer pipes often use internal heat transfer tubes, which occupy part of the internal volume of the reactor. To compensate for the loss of effective reactor volume, KLNP with internal heat exchange tubes require a larger total internal volume, which increases investment. In addition, internal heat transfer coils, usually associated with KLNP, may undesirably affect the configuration of the flow of the reaction medium inside the reactor vessel, which, consequently, leads to a loss of conversion. To increase the conversion of the product, many widespread manufacturing enterprises used a large number of SRNPs working in sequence, which further increases both financial and production costs.

Thus, there is a need for a highly efficient process for producing a polyester that reduces financial, manufacturing and operating costs while maximizing product conversion.

SUMMARY OF THE INVENTION

In one embodiment of the present invention, there is provided a method comprising: (a) subjecting an esterification reaction medium in a vertically elongated esterification reactor, and (b) optionally, optionally mixing the reaction medium in an esterification reactor in which less than about 50 percent stirring carried out by mechanical stirring.

In another embodiment of the present invention, there is provided a method comprising: (a) subjecting a first esterification reaction medium in a first esterification zone to thereby obtain a first product having a conversion of at least about 70 percent; and (b) at least a portion of the first further esterification product is subjected in a second esterification zone limited to the second esterification reactor, thereby obtaining a second product having at least 80 percent conversion, said second esterification reactor defines a fluid inlet receiving the first product and a fluid outlet discharging the second product, the fluid outlet being located at a higher height than the fluid inlet.

In yet another embodiment of the present invention, there is provided an apparatus including a reaction vessel and a large number of vertically spaced heat exchange tubes disposed in the reaction vessel. The reaction vessel is elongated along the vertical central axis of elongation. The reaction vessel determines the fluid inlet, the large number of vertically spaced fluid outlets, and the vapor outlet. The fluid inlet is located at a lower height than the vapor outlet. Fluid outlets are located above the fluid inlet and below the vapor outlet.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the present invention are described in detail below with reference to the figures, where

FIG. 1 is a block diagram of a system for a first esterification step configured in accordance with one embodiment of the present invention and suitable for use in the production of a molten polyester;

FIG. 2 is a schematic diagram of a reactor for a second esterification step configured in accordance with one embodiment of the present invention and suitable for use in the production of a molten polyester, wherein line A connects the reactor for the second esterification step of FIG. 2 to a first stage system esterification in figure 1; and

FIG. 3 is a sectional view along line 3-3 of the reactor for the second esterification step of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

The present invention can be used in the production of a molten-phase polyester capable of producing a wide variety of polyesters from various starting materials. As used herein, the term “polyester” also includes derivatives of the polyester, such as, for example, polyethers, polyethers and polyethers. Examples of molten phase polyesters that can be produced in accordance with the present invention include, but are not limited to, homopolymers and copolymers of polyethylene terephthalate (PET), PETG (PET modified with a comonomer of 1,4-cyclohexane-dimethanol (CHDM)), fully aromatic or liquid crystalline polyesters, biodegradable polyesters such as butanediol, terephthalic acid and adipic acid residues, homopolymers and copolymers of poly (cyclohexane and dimethylene terephthalate ata) and homopolymers and copolymers of CHDM and cyclohexane dicarboxylic acid or dimetiltsiklogeksandikarboksilata.

In one embodiment of the present invention, the polyester starting materials comprising at least one alcohol and at least one acid are esterified in the initial section of the process. The acidic starting material may be dicarboxylic acid and therefore the final polyester product includes one dicarboxylic acid residue having from about 4 to about 15 carbon atoms or from 8 to 12 carbon atoms. Examples of dicarboxylic acids suitable for use in the present invention may include, but are not limited to, terephthalic acid, phthalic acid, isophthalic acid, naphthalene-2,6-dicarboxylic acid, cyclohexane dicarboxylic acid, cyclohexane diacetic acid, diphenyl-4,4 ' β-dicarboxylic acid, diphenyl-3,4′-dicarboxylic acid, 2,2-dimethyl-1,3-propanolediol dicarboxylic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and mixtures thereof. In one embodiment, the acidic starting material may be the corresponding ester, for example dimethyl terephthalate instead of terephthalic acid.

The alcohol starting material may be a diol, therefore, the final polyester product may include at least one diol residue, for example, from those formed from cycloaliphatic diols having from about 3 to about 25 carbon atoms or from 6 to 20 carbon atoms. Suitable diols may include, but are not limited to, ethylene glycol (EG), diethylene glycol, triethylene glycol, 1,4-cyclohexane-dimethanol, propane-1,3-diol, butane-1,4-diol, pentane-1,5- diol, hexane-1,6-diol, neopentyl glycol, 3-methylpentanediol- (2,4), 2-methylpentanediol- (1,4), 2,2,4-trimethylpentane-diol- (1,3), hexanediol- (1,3), 1,4-dihydroxyethoxy) benzene, 2,2-bis- (4-hydroxycyclohexyl) propane, 2,4-dihydroxy-1,1,3,3-tetramethyl-cyclobutane 2,2, 4,4-tetramethyl-cyclobutanediol, 2,2-bis- (3-hydroxyethoxyphenyl) propane, 2,2-bis- (4-hydroxy-propoxyphenyl) propane, isosorbide, hydroquinone, butadiene irol- (2,2- (sulfonilbis) 4,1-phenyleneoxy) bis (ethanol), and mixtures thereof.

In addition, in one embodiment, the starting materials may include one or more comonomers. Suitable materials may include, for example, comonomers comprising terephthalic acid, dimethyl terephthalate, isophthalic acid, dimethyl isophthalate, dimethyl-2,6-naphthalenedicarboxylate, 2,6-naphthalenedicarboxylic acid, ethylene glycol, diethylene glycol, 1,4-cyclohexane 1,4-butanediol, polytetramethylene glycol, trans-DMDC, trimellitic anhydride, dimethylcyclohexane-1,4 dicarboxylate, dimethyldecalin-2,6 dicarboxylate, decalindimethanol, decahydronaphthalan 2,6-dicarboxylate, 2,6-dihydromethyl-decahydronone, enzoynuyu acid and mixtures thereof.

In accordance with one embodiment of the present invention, one or more additives can be added to the starting materials, the polyester and / or to the intermediate polyester materials in one or more places within the process. Suitable additives may include, for example, trifunctional or tetra-functional comonomers, such as trimellitic anhydride, trimethylpropane, pyromellitic dianhydride, pentaerythritol or other polyhydric acids or polyols; crosslinking or branching agents; dye; toner; pigment; carbon black; fiberglass; filler; elasticizer; antioxidant; UV absorbing compound and oxygen removing compound.

In general, in the method for producing the polyester in accordance with one embodiment of the present invention, two main sections can be used. In the first section, the reaction of the starting materials (also referred to herein as “raw materials” or “reactants”) is carried out to produce monomers and / or oligomers. In the second section, reactions are then carried out with monomers and / or oligomers to obtain the final polyester product.

If the starting materials entering the first section include acidic end groups, such as for example terephthalic acid or isophthalic acid, the first section may be called the esterification section. If the starting materials have methyl end groups, for example, such as dimethyl terephthalate or dimethyl isophthalate, the first section may be called the transesterification or trans-esterification section. For simplicity, the term “esterification” as used herein includes both esterification reactions and transesterification and ether exchange reactions. Therefore, if the first section is used for esterification, transesterification or trans-esterification, it may be called the “esterification section” of the method. In accordance with one embodiment of the present invention, the esterification can be carried out in one or more stages of the esterification section at a temperature in the range of from about 220 to about 300 ° C, or from about 235 to about 290 ° C, or from about 245 to about 280 ° C and at a pressure of less than about 25 psig (1 psig = 6894.757 Pa), or at a pressure in the range of about 1 to about 10 psig, or in the range of 2 to 5 psig. In one embodiment, the average chain length of the monomer and / or oligomer exiting the esterification section may be less than about 25, from about 1 to about 20, or from 5 to 15.

The second section of the method may be called the polycondensation section. In the polycondensation section, a one-step process can be used or it can be divided into the prepolycondensation (or prepolymerization) stage and the final (or final) polycondensation stage. Typically, polymers with longer chains can be obtained through a multi-stage polycondensation process. Typically, the polycondensation can be carried out in the polycondensation section at a temperature in the range of from about 220 to about 350 ° C. or in the range of from about 240 to about 320 ° C. and below atmospheric pressure (for example, in vacuum). When polycondensation is carried out in a two-stage process, the prepolymerization reactor (or to prepare the prepolymer) can convert the monomer leaving the esterification section into an oligomer having an average chain length in the range of from about 2 to about 40, from about 5 to about 35, or from 10 to 30. Then, the final reactor converts the mixture of oligomer and polymer into the final polymer product having the desired average chain length, usually in excess of about 30, in excess of about 50, in excess of about 75, or in excess of 90.

A multi-stage esterification section configured in accordance with one embodiment of the present invention is shown in FIGS. 1-3. In particular, FIG. 1 shows an exemplary single-stage esterification system in the first stage, and FIGS. 2 and 3 show an exemplary esterification reactor in the second stage. The multi-stage esterification section of FIGS. 1-3 will now be described in more detail.

1, a first stage esterification system 10 configured in accordance with one embodiment of the present invention typically includes a heat exchanger 12, an esterification vessel 14, a distillation column 16, and a recirculation loop 18. In general, the method carried out in the first stage esterification system 10 includes the following major steps: (1) introducing esterification materials into the heat exchanger 12; (2) heating and partial esterification of the charged materials for esterification in the heat exchanger 12; (3) introducing at least a portion of the heated and partially esterified product from the heat exchanger 12 into the esterification vessel 14; (4) further esterification of the partially esterified product from the heat exchanger 12 into the esterification vessel 14; (5) separating the liquid product from the vaporous by-product in the esterification vessel 14; (6) introducing at least a portion of the vaporous by-product from the esterification vessel 14 into a distillation column 16; (7) separating the vaporous by-product into a predominantly aqueous upper stream and a predominantly alcohol lower stream in a distillation column 16; (8) directing the recycled portion of the liquid product from the esterification vessel 14 back to the heat exchanger 12 along the recirculation loop 18; (9) during the recirculation of a portion of the liquid product flowing through the recirculation circuit 18, adding recycled alcohol to it from the distillation column 16, fresh alcohol, additive (s) and / or acid; and (10) withdrawing a portion of the liquid product from the esterification vessel 14 for further downstream processing.

As shown above, esterification in the first stage can be carried out both in the heat exchanger 12 and in the esterification vessel 14 in the system 10. Therefore, both the heat exchanger 12 and the esterification vessel 14 can be called “first stage esterification reactors”, each they are determined by a part of the “esterification zone of the first stage”. However, due to the fact that the additional function of the heat exchanger 12 can be the heating of the reaction medium processed in it, the heat exchanger 12 can also be called a “heater”, which forms a “heating zone”. In addition, since an additional function of the esterification vessel 14 may be to improve the separation of vapor and liquid, the esterification vessel 14 may also be referred to as a “separation vessel” that forms a “separation zone”. The configuration and operation of the first stage esterification system 10 shown in FIG. 1 will now be described in more detail.

As again shown in FIG. 1, the recirculated liquid product stream, discussed in more detail below, is transported through the recirculation pipe 100 of the first stage esterification system 10. As shown in FIG. 1, the following materials may be added to the recycled liquid product stream flowing through the recirculation pipe 100: (a) fresh fresh alcohol introduced through the pipeline 104, and (b) one or more additives introduced through the pipeline 106 In another embodiment, at least a portion of one or more streams in conduits 104 and / or 106 may be added to a stream exiting the esterification vessel 14 through conduit 114, which will be discussed in detail below. In yet another embodiment, at least a portion of one or more streams in conduits 104 and / or 106 may be introduced directly into recirculation pump 40, which will be discussed later. The fresh alcohol in line 104 may be any of the alcohols discussed above as being suitable for use as starting materials in the system of the present invention. In accordance with one embodiment, the alcohol may be ethylene glycol. One or more additives in conduit 106 may be any of the additives discussed above as being suitable for use in the system of the present invention.

Additional acid from line 108 can also be added to the stream flowing through line 100 for recirculation. The acid introduced into the recycle conduit 100 through conduit 108 may be any of the acids discussed above as being suitable for use as starting materials in the system of the present invention. The acid in conduit 108 may be in the form of a liquid, suspension, paste, or dry solids. In one embodiment, the acid in conduit 108 may be terephthalic acid solid particles.

In one embodiment of the present invention, the acid in conduit 108 is added to the recycle stream in conduit 100 in the form of small substantially dry solid particles (e.g., in powder form). In such an embodiment, the acid introduced into conduit 100 may contain less than about 5 percent by weight, less than about 2 percent by weight, or less than 1 percent by weight of liquid. This method of adding dry acid can eliminate the need for complex and expensive mechanically agitated tanks conventionally used to convert solid acid particles into a paste or suspension before introducing the resulting mixture into an esterification process.

As shown in FIG. 1, a pressure reducer 20 can be used to provide direct addition of the reacting solid acid to the recirculation pipe 100 without using it as a paste or suspension. In one embodiment of the present invention, the reactive solid acid may be added to the recirculation pipe 100 at the point where the pressure has been reduced by the pressure reducer 20. The pressure reducer 20 may be any device known in the art that can reduce the pressure of the main fluid stream so that material can be added to the reduced pressure stream through an opening located close to the reduced pressure zone. The ejector is one example of a device suitable for use as a pressure reducer 20.

As shown in FIG. 1, reactive solid acid in conduit 108 may be added to recirculation loop 18 downstream of the injection points of additional alcohol and additives. In addition, it may be preferable to introduce reactive solid acid into the top of the recirculation conduit 100 to accelerate the dissolution of the solid acid particles as they descend into the recycle stream. The presence of monomers and / or polyester oligomers in the recycle stream can also enhance the dissolution of solid acid particles added to the recycle line 100. In one embodiment of the present invention, the stream in the recycle line 100 can have an average chain length in the range of about 1 to about 20, from about 2 to about 18; or from 5 to 15.

Typically, the amount of alcohol and acid added to the recycle stream in the recycle conduit 100 may be any amount necessary to provide the required capacity and the desired ratio between alcohol and acid. In one embodiment of the present invention, the molar ratio of alcohol to acid in the esterification feed stream leaving the recirculation pipe 100 is in the range of from about 1.005: 1 to about 10: 1, from about 1.01: 1 to about 8: 1, or from 1.05: 1 to 6: 1.

The mixed stream leaving the recirculation conduit 100 and / or pressure reducer 20 can be introduced as an initial feed stream for esterification to the inlet 22 of the heat exchanger 12 through the supply pipe 110. In the heat exchanger 12, the supplied and reactive esterification medium is heated and subjected to esterification conditions. According to one embodiment of the present invention, an increase in the temperature of the reaction medium between the inlet 22 and the outlet 24 of the heat exchanger 12 can be at least about 50 ° F (10 ° C), at least about 75 ° F (23.89 ° C), or at least 85 ° F (29.41 ° C). In general, the temperature of the esterification medium supplied to the inlet 22 of the heat exchanger can be in the range from about 220 to about 260 ° C., from about 230 to about 250 ° C., or from 235 to 245 ° C. Typically, the temperature of the esterification product exiting the outlet 24 of the heat exchanger 12 may be in the range of from about 240 to about 320 ° C., from about 255 to about 300 ° C., from 275 to 290 ° C. The reaction medium in the heat exchanger 12 can be maintained at a pressure in the range of from about 5 to about 50 psig, from about 10 to about 35 psig, or from 15 to 25 psig (1 psig = 0.0703 kg / cm ² ).

As discussed above, the heat exchanger 12 can also be considered an esterification reactor, since at least part of the reaction medium flowing through it can undergo esterification. The amount of esterification carried out in accordance with the present invention can be quantified as “conversion”. Here, the term “conversion” is used to describe the properties of the liquid phase of a stream that is esterified, with the conversion of the esterified stream indicating the percentage of the original acid end groups that have been converted (ie, esterified) to ether groups. The conversion can be quantified by the number of converted end groups (i.e., alcohol end groups) divided by the total number of final groups (i.e. alcohol plus acid end groups), with the result of the division being expressed as a percentage. Although conversion is used here, it should be understood that the average chain length, which describes the average number of monomer units that the compound includes, may also be suitable for describing the flow characteristics of the present invention.

According to one embodiment, the esterification reaction carried out in the heat exchanger 12 can increase the conversion of the reaction medium between inlet 22 and outlet 24 by at least about 5, at least about 10, at least about 15, at least about 20, at least about 30, or at least 50 percent. Typically, the esterification feed stream introduced into the inlet 22 of the heat exchanger 12 has a conversion of less than about 90 percent, less than about 75 percent, less than 50 percent, less than 25 percent, less than 10 percent or less than 5 percent, and the esterification product stream output from the outlet 24 of the heat exchanger 12 has a conversion of at least about 50 percent, at least about 60 percent, at least about 70 percent, at least about 75 percent, at least about 80 percent, at least D about 85 percent, at least about 95 percent or at least 98 percent.

In one embodiment of the present invention, the esterification reaction carried out in the heat exchanger 12 proceeds with a significantly shorter residence time in comparison with well-known esterification methods. For example, the average residence time of the reaction medium flowing through the heat exchanger 12 may be less than about 60 minutes, less than about 45 minutes, less than about 35 minutes, or less than 20 minutes. This relatively short residence time can be achieved even with high productivity for commercial purposes. Thus, in one embodiment, the product stream is withdrawn from the outlet 24 of the heat exchanger 12 at a rate of at least about 10,000 pounds per hour (1 lb / h = 0.454 kg / h), at least about 25,000 pounds per hour, at least about 50,000 pounds per hour or at least 100,000 pounds per hour (45,360 kg / hour).

We now turn to the special configuration of the heat exchanger 12. In accordance with one embodiment of the present invention, the heat exchanger 12 may be a horizontally elongated shell-and-tube heat exchanger. Internal passages for the passage of liquid through them can be created by heat exchange tubes through which the reaction medium flows, and it is heated and esterified. These internal passages can be considered as a “first esterification zone” of the first stage esterification system 10. Typically, the total volume of internal passages for flow through a heat exchanger can be in the range of about 10 to about 1,500 cubic feet (1 ft ³ = 0.028 m ³ ), about 100 to about 800 cubic feet, and 200 to 600 cubic feet. The average inner diameter of individual heat exchanger tubes may be less than 4 inches (1 inch = 2.54 cm) or range from about 0.25 to about 3 inches or from 0.5 to 2 inches.

As shown in FIG. 1, a stream of heated heat transfer medium (TPS) can flow into the side of the casing of the heat exchanger 12 and at least partially surround at least a portion of the heat transfer tubes to heat the reaction medium flowing through them. In one embodiment of the present invention, the heat transfer coefficient related to heating the reaction medium in the heat exchanger 12 may be in the range of about 0.5 to about 200 BTU (1 BTU = 0.252 kcal) per hour per ° F per square foot (1 BTU / h . ° F.ft ² = 1.507 kcal / m ² .hour ° C), from about 5 to about 100 BTU / h. ° F.ft ² or from 10 to 50 BTU / h. ° F.ft ² . The total amount of heat transferred to the reaction medium in the heat exchanger 12 can range from about 100 to about 5,000 BTU / lb of reaction medium, from about 400 to about 2,000 BTU / lb, or from 600 to 1,500 BTU / lb.

As shown in FIG. 1, a partially esterified product exiting outlet 24 may be transported to the esterification vessel 14 through line 112. The partially esterified stream in line 112 may be introduced into the internal volume of the esterification vessel 14 through a fluid inlet 26. As already discussed above, in the container 14 for esterification, the partially esterified stream is subjected to further esterification and phase separation. Thus, the internal volume limited within the esterification vessel 14 can be considered as an “esterification zone” and / or as a “separation zone”. In general, the reaction medium in the esterification vessel 14 flows substantially horizontally through the internal volume. When the reaction medium flows from inlet 26 and is esterified, vaporous by-products escape from the liquid phase and usually flow over the liquid phase. The separated liquid product may exit the esterification vessel 14 through the liquid outlet 28, and the separated vaporous by-product may exit the esterification vessel 14 through the steam outlet 30.

The esterification reaction carried out in the esterification vessel 14 can increase the degree of conversion of the reaction medium processed therein, therefore, the liquid product exiting the liquid outlet 28 has a degree of conversion that is at least about 1 percent, at least about 2 percent, or at least 5 percent, higher than the degree of conversion of the fluid stream entering fluid inlet 26. In general, the liquid product exiting the fluid outlet 28 of the esterification vessel 14 may have a conversion of at least about 80 percent, at least about 85 percent, at least about 90 percent, at least 95 percent, or at least about 98 percent.

The conversion achieved in the esterification vessel 14 can occur during a relatively short residence time and with little or no heat input. For example, the average residence time of the reaction medium in the esterification vessel 14 may be less than about 200 minutes, less than about 60 minutes, less than about 45 minutes, less than about 30 minutes, or less than 15 minutes. In addition, the amount of heat transferred to the reaction medium in the esterification vessel 14 may be less than about 100 BTU / lb of reaction medium (BTU / lb), less than about 20 BTU / lb, less than about 5 BTU / lb, or less than 1 BTU / lb .

With minimal heat input or without heat input to the esterification vessel 14, the average temperature of the liquid product exiting the liquid outlet 28 from the esterification vessel 14 can be in the range of about 50 ° C, about 30 ° C, about 20 ° C, or 15 ° C of the average temperature of the liquid entering the esterification vessel 14 through the fluid inlet 26. In general, the average temperature of the liquid product exiting the fluid outlet 28 for the esterification vessel 14 may be in the range from about 220 to about 320 ° C., from about 240 to about 300 ° C., or from about 259 to about 275 ° C.

We turn again to the special configuration of the container 14 for esterification. In the embodiment shown in FIG. 1, the esterification vessel 14 is a substantially empty, non-stirred, unheated, typically cylindrical horizontally elongated vessel. The esterification vessel 14 may have a length to diameter ratio of less than about 10: 1, in the range of from about 1.25: 1 to about 8: 1, from about 1.5: 1 to about 6: 1, or from 2: 1 to 4 5: 1. In one embodiment, the fluid inlet 26 and the steam outlet 30 are separated from one another in such a way that sufficient esterification is provided and separation / separation of the vapor, liquid and foam phases is enhanced. For example, the fluid outlet 28 and the steam outlet 30 can be horizontally separated from the fluid outlet 26 by a distance of at least about 1.25 D, at least about 1.5 D, or at least 2.0 D. In addition, the fluid outlet 28 and the steam outlet 30 can be vertically separated from each other by a distance of at least about 0.5 D, at least about 0.75 D, or at least 0.95 D.

As shown in FIG. 1, the esterification vessel 14 may include a fluid dispenser 32 for efficiently distributing the supplied liquid to the esterification vessel 14. In the embodiment shown in FIG. 1, the fluid dispenser is a substantially simply horizontally positioned conduit having a downward curved end that forms a fluid inlet 26 with a downward orientation. Alternatively, the fluid dispenser 32 may provide a large number of openings for discharging a partially esterified feed liquid to a large number of horizontally distributed locations in the esterification vessel 14. In one embodiment of the present invention, the average depth of the reaction medium in the esterification vessel 14 is maintained at a level of less than about 0.75D, less than about 0.50D, less than about 0.25D, or less than 0.15D when it moves substantially horizontally through the vessel 14 esterification.

As shown in FIG. 1, when entering the esterification vessel 14, the reaction medium exiting the liquid distributor 32 may begin to foam when vapor bubbles are released from the liquid portion of the reaction medium. In general, the formation of foam may decrease along the length of the esterification vessel 14 when steam is separated from (released from) the liquid phase of the reaction medium, so that in one embodiment, substantially no vapor leaves the liquid outlet 28 and / or the vapor exit 30 of the vessel 14 for esterification.

In order to ensure that substantially no vapor escapes from the steam outlet 30 in the esterification vessel 14, a downward directed wall 34 may be used in the esterification vessel 14. The wall 34 may generally be located between the fluid inlet 26 and the outlet 30 for the steam of the esterification vessel 14, but closer to the steam outlet 30 than to the fluid inlet 26. The septum 34 may be directed downward from the top of the esterification vessel 14, close to the steam outlet 30, and may be actuated to physically block the foam flow, if any, directed toward the steam outlet 30. In one embodiment of the present invention, the baffle 34 may be a lower edge vertically spaced at least about 0.25 D, at least about 0.5 D, or at least 0.75 D from the bottom of the esterification vessel 14. In the embodiment shown in FIG. 1, the baffle includes a downwardly extending portion 36 and an elongatingly extending portion 38. An elongatedly extending portion 36 may be directed downward from a portion adjacent to the steam outlet 30, and the elongated portion 38 may be is directed in the transverse direction from the lower end of the downwardly extending portion 36 to a portion usually located under the steam outlet 30.

The total internal volume limited by the esterification tank 14 may depend on a number of factors, including, for example, the general hydrodynamic requirements of the esterification system 10. In one embodiment of the present invention, the total internal volume of the esterification vessel 14 may be at least about 25 percent, at least about 50 percent, at least about 75 percent, at least about 100 percent, or at least 150 percent of the total internal the volume of the recirculation loop 18, described in more detail below. In yet another embodiment of the present invention, the total internal volume of the esterification vessel 14 may be at least about 25 percent, at least about 50 percent, at least about 75 percent, or at least 150 percent of the total internal volume of the recirculation loop 18, passages for the flow of fluid in the heat exchanger 12 and the pipe 112 for the product.

As again shown in FIG. 1, a steam stream exiting the steam outlet 30 for the esterification vessel 14 through line 120 may be directed to the distillation column fluid inlet 42. The vaporous product stream in conduit 120 may include water and alcohol. Water and alcohol can be substantially separated from each other in the distillation column 16, thereby thereby obtaining an upper stream of predominantly water vapor leaving the distillation column 16 through an upper outlet 44, and a lower liquid stream of predominantly alcohol leaving the distillation column 16 through bottom outlet 46. The distillation column 16 may be any device capable of dividing the stream into a predominantly upper vapor product and a predominantly lower liquid product based on relative volatility Tei components of the feed stream. The distillation column 16 may include internal devices, such as, for example, trays, random nozzles, structured nozzles, or any combination thereof.

According to one embodiment of the present invention, an overhead stream of predominantly water vapor leaving the distillation column 16 through an overhead outlet 44 may include at least about 50 mole percent, at least about 60 mole percent, or at least 75 mole percent of water . The upper vaporous product discharged from the outlet 44 of the distillation column 16 may be sent via line 122 for further processing, storage or disposal, for example, to a waste water treatment apparatus or to a disposal means using, for example, combustion.

Advantageously, the alcoholic bottom liquid stream exiting the distillation column 14 through the bottom outlet 46 may include at least about 50 mole percent, at least about 60 mole percent, or at least 75 mole percent of an alcohol (e.g. ethylene glycol). In one embodiment of the present invention, the predominantly alcohol stream discharged from the bottom outlet 46 of the distillation column 16 may have a temperature of at least about 150 ° C, in the range of from about 175 to about 250 ° C, or from 190 to 230 ° C, and a pressure in the range from about 0.25 to about 50 psig, from about 0.5 to about 35 psig, or from 1 to 25 psig. As shown in FIG. 1, the liquid stream discharged from the bottom outlet 46 of the distillation column can be sent via line 124 for further processing, storage and / or secondary use.

As shown in FIG. 1, a liquid ester product may be discharged from the fluid outlet 28 of the esterification vessel 14 and may then be introduced into the recirculation circuit 18. The recirculation loop 18 defines the passageways for the fluid to flow from the fluid outlet 28 to the esterification tank 14 to the inlet 22 of the heat exchanger 12. The recirculation loop 18 typically includes a liquid product line 114, a recirculation pump 40, a discharge pipe 116 from the pump, a recirculation pipe 100, a pressure reducer 20 and a supply pipe 110. The liquid ether product discharged from the esterification vessel 14 may first flow through the product pipe 114 to the suction side of the recirculation pump and 40. The stream leaving pump 40 may be passed through the outlet pipe 116 from the pump and then divided into a product part transported through the ether product pipe 118 and a recirculation part transported through the recirculation pipe 100. Separating the stream exiting pump 40, can be carried out so that the ratio of the specific mass flow rate of the recirculation part in the pipeline 100 to the specific mass flow rate of the product part in the pipe 118 is in the range from about 0.2 5: 1 to about 30: 1, from about 0.5: 1 to about 20: 1, or from 2: 1 to 15: 1. As discussed above, the recycle portion in conduit 100 can ultimately be used as the initial supply to the heat exchanger 12 after adding fresh alcohol through conduit 104, additives (additives) through conduit 106 and / or acid through conduit 108.

The product portion of the liquid ether product in conduit 118 may be directed to a downstream location for further processing, storage, or other use. In one embodiment, at least a portion of the product portion in conduit 118 may be further esterified in a second stage esterification reactor, described in more detail below.

As now shown in FIG. 2, a portion of the product from the first stage esterification system 10 (FIG. 1) can be directed to the fluid inlet 48 of the second stage esterification reactor 50 (FIG. 2) through line A. In the second stage reactor 50, the reaction the medium is heated and exposed to esterification conditions. However, in contrast to the complex and time-consuming maintenance and repair of tank reactors with continuous mixing of the prior art, the second stage esterification reactor 50 can be a simple and reliable reaction vessel that provides little mixing or does not require mechanical stirring of the reaction medium processed therein. In one embodiment of the present invention, less than about 50 percent, less than about 25 percent, less than about 10 percent, less than about 5 percent of mechanical stirring is provided, or essentially no stirring of the reaction medium in the second stage esterification reactor 50 is required. In another embodiment, the second stage esterification reactor 50 is not provided with a stirrer, as shown in FIG.

In one embodiment, the heat provided within the second stage esterification reactor 50 increases the temperature of the reaction medium by at least about 5 ° F, at least about 10 ° F, or at least 25 ° F. Typically, the inlet temperature of the reaction medium may be in the range from about 200 to about 300 ° C., from about 225 to about 280 ° C., or from 240 to 270 ° C., and the outlet temperature may be in the range from about 230 to about 310 ° C. , from about 240 to about 290 ° C. or from 245 to about 275 ° C. The upper pressure in the second stage esterification reactor 50 may be maintained at a level of less than about 25 psig, less than about 15 psig, or less than 5 psig.

As a result of the esterification carried out in the second stage esterification reactor 50, the stream entering the second stage esterification reactor 50 through the fluid inlet 48 can undergo a conversion increase of at least about 2 percent, at least about 5 percent, or at least 10 percent between the fluid inlet 48 and the liquid outlet 52 in the second stage esterification reactor 50. Typically, the stream entering the fluid inlet 48 of the second stage esterification reactor 50 may have a conversion of at least about 70 percent, at least about 75 percent, or at least 80 percent, and the stream leaving the second stage esterification reactor 50 through conduit 130, may have a conversion of at least about 80 percent, at least about 90 percent, at least about 95 percent, or at least 98 percent. In general, the residence time of the reaction medium in the reaction vessel 50 may be more than about 45 minutes, more than about 60 minutes, or more than about 70 minutes.

We turn now to the special configuration of the second stage esterification reactor 50. In one embodiment shown in FIG. 2, the second stage esterification reactor 50 is a substantially cylindrical vertically elongated non-agitated vessel with a maximum diameter (D) and a ratio of its height to diameter (H: D) in the range of about 1.15: 1 to about 10: 1, or from about 1.25: 1 to about 8: 1, or from 1.4: 1 to 6: 1. The second stage esterification reactor 50 may include a lower end wall 54, a generally cylindrical side wall 56 and an upper end wall 58, which respectively form a fluid inlet 48, at least one fluid outlet 52 and a steam outlet 60. In one embodiment, the cylindrical side wall 56 may include a large number of vertically spaced fluid outlets, shown in FIG. 2, as the upper, middle, and lower fluid outlets 52a, 52b, 52c. The fluid inlet 48, the liquid outlets 52a-c and the steam outlet 60 can be separated from one another in such a way as to maximize the conversion of the reaction medium flowing through the second stage esterification reactor 50 in comparison with the continuous stirred tank esterification reactors level of this technique. For example, the fluid inlet 48 may be located at a lower height than the outlet 52a-c, and the steam outlet 60 may be located at a higher height than the liquid outlet 52a-c. In accordance with one embodiment, the fluid inlet 48 may be located in a lower portion (e.g., a lower one third), fluid outlets 52a-c may be located in the middle and / or upper portions (e.g., in the middle one third and / or in the upper two-thirds), and the steam outlet 60 may be located in the upper section (for example, in the upper one-third) of the second stage esterification reactor 50.

Now, as shown in FIG. 3, in one embodiment, the fluid inlet 48 and / or the liquid outlets 52 can be radially and / or circumferentially separated from one another so as to maximize the degree of conversion of the reaction medium in the second esterification reactor 50 stages in comparison with well-known continuous stirred tank reactors. As shown in FIG. 3, the second stage esterification reactor 50 can determine the vertical central axis of the extension 62, from which the fluid inlet 48 and fluid outlets 52 can be radially spaced apart at respective distances r _i and r _o . In one embodiment, r _i may be at least about 0.15D, at least about 0.25D, or at least 0.4D, where D is the maximum horizontal size of the volume bounded within the esterification reactor 50. In one embodiment, r _o may be at least about 0.45D or at least 0.5D. In addition to the radial distance from the central axis 62, the fluid inlet 48 and the fluid outlets 52 can be circumferentially separated from each other by an angle Θ, as shown in FIG. 3. In one embodiment, the angle Θ may be at least about 45 °, at least about 90 °, at least about 120 °, or at least about 175 ° C.

Again, as shown in FIG. 2, the second stage esterification reactor 50 can provide heat to the reaction medium flowing through a plurality of vertically spaced heat transfer elements, typically located above the fluid inlet 48 and under the steam outlet 60. In one embodiment, the heat transfer elements may be heat transfer tubes. The tubes may be arranged in vertically spaced groups of two or more, such as the upper, middle and lower groups 64a, 64b, and 64c, as shown in FIG. Each group of heat transfer tubes can receive a stream of heated heat transfer medium (TPS), respectively, through the upper, middle and lower inlets 66a, 66b, and 66c for TPS. TPN then flows through the tubes to heat the reaction medium in the second stage esterification reactor 50. In one embodiment of the present invention, a heat transfer coefficient related to heating the reaction medium in the second stage esterification reactor 50 may range from about 10 to about 150 BTU per hour per square foot per ° F (BTU / h.ft ^2. ° F) , from about 25 to about 100 BTU / h.ft ^2. ° F, from about 35 to 80 BTU / h.ft ^2. ° F. The total amount of heat transferred to the reaction medium in the second stage esterification reactor 50 by the heat transfer elements may range from about 100 to about 5,000 BTU per pound of reaction medium (BTU / lb), from about 400 to about 2,000 BTU / lb, or from 600 to 1500 BTU / lb. The cooled TPN is discharged from the upper, middle and lower groups of heat exchanger tubes 64a-c through the corresponding outputs for the TPN (not shown) and then can be recycled through the TPN system.

The flow of TPNs to heat exchange tube groups 64a-c can be controlled by the upper, middle, and lower TPNs by valves 68a, 68b, and 68c. In one embodiment of the present invention, the groups of heat transfer tubes 64a-c can be independently controlled so that one or more groups can provide heating of the reaction medium in the second stage esterification reactor 50 and one or more groups of tubes does not substantially provide heating. By independently controlling one or more groups of heat exchange tubes 64a-c, it is possible to increase the operational flexibility of the second stage esterification reactor 50 above the operational flexibility of the case reactors with continuous mixing of the prior art. For example, as shown in FIG. 2, the upper TPS valve 68a may be closed to thereby prevent the flow of heated TPS into the upper tube group 64a when the level of reaction medium 72 in the second stage esterification reactor 50 is lower than in the upper group 64a handsets. The ability of the second stage esterification reactor 50 to operate at various levels of the reaction medium is in direct contrast with the prior art continuous stirred tank reactors, which usually operate at a constant level of the reaction medium, to keep the heat transfer tubes completely submerged all the time during the operation.

Turning again to FIG. 2, it is shown that a predominantly vaporous product can exit the second stage esterification reactor 50 through a steam outlet 60. In one embodiment of the present invention, the predominantly vaporous product may include water and / or alcohol, for example, such as ethylene glycol. After exiting the esterification reactor 50 of the second stage, the vapor stream flows into the pipeline 128, after which it can be sent for further processing, storage and / or disposal.

As shown in FIG. 2, the liquid product may be withdrawn from the second stage esterification reactor 50 through one or more liquid outlets 52a-c. In one embodiment in which one or more groups of heat exchanger tubes 64a-c are independently controlled, one or more respective outputs for the liquid product can also be isolated by using product valves 70a-c. For example, when the level of the reaction medium is below the upper group of heat transfer tubes 64a and the tubes are isolated from the heat supply, as described above, the upper liquid outlet 52a can be further insulated by closing the upper product valve 70a, as shown in FIG. 2. Similarly, the ability to independently shut off one or more fluid outlets provides additional operational flexibility to the second stage esterification reactor 50.

The liquid esterification product exits the second stage esterification reactor 50 via line 130 and can then be sent to storage or for further processing, for example, to the polycondensation section located downstream.

NUMERIC BANDS

In the present description, numerical ranges are used to quantify certain parameters related to the invention. It should be understood that in the presence of numerical ranges, the latter should be considered as providing literal support for limiting patent claims that only define the upper limit of the range. For example, a disclosed numerical range of 10 to 100 provides literal support for a clause that says “greater than 10” (without upper limits) and for a clause that says “less than 100” (without lower limits).

DEFINITIONS

The terms used here: “a, an, the and said” mean one or more.

As used herein, the term “mixing” refers to work performed in a reaction medium that causes fluid movement and / or mixing.

The term “and / or”, as used herein, when used in a list of two or more items, means that any one of the items listed can be used on its own or any combination of two or more items can be used. For example, if a composition is described containing components A, B and / or C, then this composition may contain only A, only B, only C; a combination of A and B, a combination of A and C, a combination of B and C, or a combination of A, B and C.

As used herein, the terms “including”, “includes” and “include” are transient non-limiting terms used to transition from an item indicated before the term to one item or item listed after the term where the item or items, listed after the transitional term are not necessary and the only elements that make up the subject.

As used herein, the terms “comprising”, “comprises” and “comprise” have the same non-limiting meanings as “including”, “includes” and “include” above.

As used herein, the term “distillation separation” refers to the separation of one or more chemicals from one or more other chemicals based on the relative volatilities of the substances to be separated.

As used herein, the terms “having”, “has” and “have” have the same non-limiting meanings as “including”, “includes” and “include” above.

As used herein, the term “reaction medium” refers to any medium that undergoes a chemical reaction.

As used herein, the term “residue” refers to a part that is a product obtained from chemicals in a particular chemical reaction system or upon subsequent formation, or a chemical product, whether or not that part is actually obtained from these chemicals.

FORMULA NOT LIMITED TO CONSIDERED EMBODIMENTS

The preferred forms of the invention described above should be used only as an illustration, and they should not be used in a limiting sense in interpreting the scope of the present invention. Those skilled in the art can easily make changes to the above exemplary embodiments without departing from the meaning of the present invention.

The inventors here declare their intention to rely on the Doctrine of Equivalents for a reasonably fair determination and assessment of the scope of the present invention, which applies to any apparatus that does not materially go beyond the literal limits of the invention as defined by the following claims.

Claims (19)

1. A method of esterification of the reaction medium in the production of polyesters in the molten phase, comprising the steps of:
(a) subjecting the esterification reaction medium in a vertically elongated esterification reactor, wherein said esterification reactor forms one vessel having a fluid inlet and at least two separate outlets containing a liquid outlet through which the reaction medium is discharged from the specified reactor for esterification, and the exit for steam through which the vaporous by-product of esterification is discharged from the reactor for esterification, and the specified exit for steam is located on the same tank for pain higher than the specified outlet for the liquid, and the specified inlet for the fluid is located at a lower height than the outlet for the liquid, and moreover, the specified reactor for esterification provides heat to the reaction medium inside; and
(b) said reaction medium in said esterification reactor is not mechanically stirred, or if mechanically mixed, less than about 50% of said stirring of the reaction medium is provided by mechanical stirring. 2. The method according to claim 1, wherein the reaction medium entering the fluid inlet has an initial conversion of at least about 70%. 3. The method of claim 2, wherein the reaction medium discharged through the liquid outlet has a final conversion of at least about 80%. 4. The method according to claim 3, in which the specified initial conversion is at least about 75% and the specified final conversion is at least about 85%. 5. The method according to claim 1, wherein said esterification reactor has a height to diameter ratio ranging from about 1.15: 1 to about 10: 1. 6. The method according to claim 1, wherein said esterification reactor provides a fluid inlet and a liquid outlet, wherein at least a first portion of said reaction medium enters said esterification reactor through said fluid inlet and, at least a second part of said reaction medium is discharged from said esterification reactor through said liquid outlet, said fluid inlet being located at a lower height than said liquid outlet. 7. The method according to claim 6, wherein said fluid inlet is located on the lower one-third of said esterification reactor, and said liquid outlet is located in the upper two-thirds of said esterification reactor. 8. The method according to claim 6, in which the specified reactor for esterification determines the vertical Central axis of elongation, while the specified output for the fluid is radially spaced from the specified Central axis. 9. The method according to claim 1, wherein said esterification reactor provides a fluid inlet and a plurality of vertically spaced fluid outlets, wherein at least a first portion of said reaction medium enters said esterification reactor through said fluid inlet a medium, wherein at least a second part of said reaction medium is discharged from said esterification reactor through one or more of said liquid outlets, said said fluid inlet being located at a smaller th elevation than said outlet for liquid. 10. The method according to claim 1, further comprising heating said reaction medium in said esterification reactor during said esterification, wherein said heating is provided by a plurality of vertically spaced heat transfer elements and said vertically spaced heat transfer elements are configured to be independently controlled in this way, that one or more of these heat exchange elements can provide heating of the specified reaction medium, while one or more others of said heat exchange elements may not provide heating said reaction medium. 11. The method according to claim 1, in which the specified reaction medium essentially does not receive mechanical stirring during the specified esterification. 12. The method according to claim 1, in which the residence time of the specified reaction medium in the specified reactor for esterification is more than about 45 minutes and it is carried out at a temperature in the range from about 200 to about 300 ° C. 13. The method of esterification of the reaction medium in the production of polyesters in the molten phase, comprising the steps of:
(a) subjecting the first esterification reaction medium to a first esterification zone formed by a first esterification reactor having a fluid inlet, a liquid outlet and a steam outlet, thereby obtaining a first product having a conversion of at least about 70%, and a vaporous by-product exiting the first esterification reactor through a steam outlet at said first esterification reactor; and
(b) at least a portion of said first product is further esterified in a second vertically elongated esterification zone formed by a second esterification reactor having a fluid inlet and at least two separate outlets containing a liquid outlet and an outlet for steam, thereby obtaining a second product having a conversion of at least about 80 percent withdrawn from said second esterification reactor through a liquid outlet in a second esterification reactor, which is located at a higher height than the fluid inlet and vaporous by-product discharged from the second esterification reactor through the steam outlet at the second esterification reactor, said second esterification reactor providing heat to the reaction medium, said reaction medium in said second reactor for esterification, they are either not mechanically mixed or, if mechanically mixed, less than about 50% of the specified mixing of the reaction medium is provided by mechanical mixing. 14. The method of claim 13, wherein said second esterification reactor defines a vertical central axis, wherein said second esterification reactor has a maximum horizontal diameter (D), and the fluid outlet of said second esterification reactor is radially at least at least 0.4D from said central axis and the fluid inlet of said second esterification reactor is radially at least 0.15D away from said central axis, said fluid inlet of said second p The esterification reactors and the liquid outlet of said second esterification reactor are circumferentially spaced apart from each other by at least about 90 °. 15. The method according to item 13, wherein said second esterification reactor provides a plurality of vertically spaced fluid outlets for discharging at least a portion of said second product, wherein the fluid inlet of said second esterification reactor is located at a lower height, than the fluid outlets of said second esterification reactor. 16. The method according to item 13, in which the specified reaction medium essentially does not receive mechanical stirring in the specified second reactor for esterification. 17. An apparatus for esterification of the reaction medium in the production of polyesters in the molten phase, including: a reaction vessel and a plurality of vertically spaced heat-exchange tubes located in said reaction vessel, wherein said reaction vessel is elongated along a vertical central axis of elongation and provides an entrance for fluid medium, a plurality of vertically spaced outlets for liquid and an outlet for steam, wherein said inlet for fluid is located at a lower height than said you a steam path, and said liquid outlets are located at a height which is higher than the fluid inlet and lower than the steam outlet, and said reaction vessel is not provided with a mechanical stirrer. 18. The apparatus according to claim 17, further comprising an upstream heat exchanger and an upstream separating vessel, wherein said upstream heat exchanger forms an inlet of a heat exchanger and an outlet of a heat exchanger, said upstream said separating vessel forming a separator fluid inlet, separate steam outlet and separate liquid outlet, said heat exchanger outlet and said fluid separating inlet communicating with each other by t pile medium, said separated liquid outlet and said fluid inlet of said reaction vessel are in fluid communication, said separated liquid outlet and said exchanger inlet in fluid communication with each other. 19. The apparatus of claim 18, wherein said separating container is horizontally elongated.

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